1. Field of the Invention
Embodiments of the invention generally relate to an apparatus and a method for depositing materials, and more particularly to an atomic layer deposition chamber configured to deposit a material during a plasma-enhanced process.
2. Description of the Related Art
In the field of semiconductor processing, flat-panel display processing or other electronic device processing, vapor deposition processes have played an important role in depositing materials on substrates. As the geometries of electronic devices continue to shrink and the density of devices continues to increase, the size and aspect ratio of the features are becoming more aggressive, e.g., feature sizes of 0.07 μm and aspect ratios of 10 or greater. Accordingly, conformal deposition of materials to form these devices is becoming increasingly important.
While conventional chemical vapor deposition (CVD) has proved successful for device geometries and aspect ratios down to 0.15 μm, the more aggressive device geometries require an alternative deposition technique. One technique that is receiving considerable attention is atomic layer deposition (ALD). During an ALD process, reactant gases are sequentially introduced into a deposition chamber containing a substrate. Generally, a first reactant is pulsed into the deposition chamber and is adsorbed onto the substrate surface. A second reactant is pulsed into the deposition chamber and reacts with the first reactant to form a deposited material. A purge step is typically carried out between the delivery of each reactant gas. The purge step may be a continuous purge with the carrier gas or a pulse purge between the delivery of the reactant gases. Thermally induced ALD processes are the most common ALD technique and use heat to cause the chemical reaction between the two reactants. While thermal ALD processes work well to deposit some materials, the processes often have a slow deposition rate. Therefore, fabrication throughput may be impacted to an unacceptable level. The deposition rate may be increased at a higher deposition temperature, but many chemical precursors, especially metal-organic compounds, decompose at elevated temperatures.
Plasma-enhanced ALD (PE-ALD) may be used to form various materials. In some examples of PE-ALD processes, a material may be formed from the same chemical precursors as a thermal ALD process, but at a higher deposition rate and a lower temperature. Although several variations of techniques exist, in general, a PE-ALD process provides that a reactant gas and a reactant plasma are sequentially introduced into a deposition chamber containing a substrate. The first reactant gas is pulsed into the deposition chamber and is adsorbed onto the substrate surface. Thereafter, the reactant plasma is pulsed into the deposition chamber and reacts with the first reactant gas to form a deposited material. Similarly to a thermal ALD process, a purge step may be conducted between the delivery of each of the reactants. While PE-ALD processes overcome some of the shortcomings of thermal ALD processes due to the high degree of reactivity of the reactant radicals within the plasma, PE-ALD processes have many limitations. PE-ALD process may cause plasma damage to a substrate (e.g., etching), be incompatible with certain chemical precursors and require additional hardware.
Therefore, there is a need for an apparatus and a process for depositing a material on a substrate by a vapor deposition technique, such as by a PE-ALD process.